linux-ext4 - Re: [RFCv2 4/4] ext4: Move ext4_fiemap to use iomap infrastructure

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Date:   Wed, 29 Jan 2020 11:49:38 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     jack@...e.cz, tytso@....edu, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        hch@...radead.org, cmaiolino@...hat.com
Subject: Re: [RFCv2 4/4] ext4: Move ext4_fiemap to use iomap infrastructure

Hello Darrick,

On 1/28/20 8:58 PM, Darrick J. Wong wrote:
> On Tue, Jan 28, 2020 at 03:48:28PM +0530, Ritesh Harjani wrote:
>> Since ext4 already defines necessary iomap_ops required to move to iomap
>> for fiemap, so this patch makes those changes to use existing iomap_ops
>> for ext4_fiemap and thus removes all unwanted code.
>>
>> Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com>
>> ---
>>   fs/ext4/extents.c | 279 +++++++---------------------------------------
>>   fs/ext4/inline.c  |  41 -------
>>   2 files changed, 38 insertions(+), 282 deletions(-)
>>
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index 0de548bb3c90..901caee2fcb1 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
> 
> <snip> Just a cursory glance...
> 
>> @@ -5130,40 +4927,42 @@ static int ext4_xattr_fiemap(struct inode *inode,
>>   				EXT4_I(inode)->i_extra_isize;
>>   		physical += offset;
>>   		length = EXT4_SB(inode->i_sb)->s_inode_size - offset;
>> -		flags |= FIEMAP_EXTENT_DATA_INLINE;
>>   		brelse(iloc.bh);
>>   	} else { /* external block */
>>   		physical = (__u64)EXT4_I(inode)->i_file_acl << blockbits;
>>   		length = inode->i_sb->s_blocksize;
>>   	}
>>   
>> -	if (physical)
>> -		error = fiemap_fill_next_extent(fieinfo, 0, physical,
>> -						length, flags);
>> -	return (error < 0 ? error : 0);
>> +	iomap->addr = physical;
>> +	iomap->offset = 0;
>> +	iomap->length = length;
>> +	iomap->type = IOMAP_INLINE;
>> +	iomap->flags = 0;
> 
> Er... external "ACL" blocks aren't IOMAP_INLINE.

Sorry, I should have mentioned about this too in the cover letter.
So current patchset is mainly only converting bmap & fiemap to use iomap 
APIs. Even the original implementation does not have external ACL block
implemented for xattr_fiemap.

Let me spend some time to implement it. But I would still like to keep
that as a separate patch.

But thanks for looking into it. There's this point 2.a & 2.b mentioned 
in the cover letter where I could really use your help in understanding
if all of that is a known behavior from iomap_fiemap side
(whenever you have some time of course :) )

-ritesh